Various methods have been used to enclose corrosive materials such as cathode materials or electrolytes with lithium. This is particularly the case in the manufacture of batteries. Primary cells having charge transfer complexes, such as iodine-containing material are generally well known. High energy density batteries utilizing a lithium anode and cathode or organic material such as polycyclic aromatic compounds, organic polymers, heterocyclic nitrogen containing compounds and the like and iodine have been disclosed. U.S. Pat. No. 3,660,163. Additionally, cxthode compositions comprising a mixture of iodine and poly-2-vinylpyridine . nI.sub.2 or poly-2-vinylquinoline. nI.sub.2, wherein n = 2-15 have been taught; U.S. Pat. No. 3,674,562, incorporated herein by reference. Cathode material of this latter type is typically a pliable, plastic-like solid having a flowable viscosity.
Lithium halide batteries of the present invention are typically used with implantable prosthetics such as cardiac pacemakers. For such application, it is necessary that the battery be physically small and highly reliable. To attain high reliability, not only is the design of the battery itself of great importance, but the methods of manufacture can play an extremely important part in achieving high reliability.
Many problems can arise during the manufacture or assembly of primary cells and, in particular, lithium halide cells, including obtaining satisfactory sealing of the depolarizer within the container. In many processes, it is difficult if not impossible to determine whether a battery will leak until it has been completely assembled with its hermetic seal. Failure to provide a leak-proof seal results in the necessity to discard the battery.
To overcome many of the problems that can arise in the manufacture of lithium-halogen batteries, a method has been proposed, U.S. Pat. Application Ser. No. 666,161, filed Mar. 12, 1975, now U.S. Pat. No. 4,010,043, wherein the cell includes a receiving vessel made of lithium which functions as the anode and into which a cathode material is poured in the heated state. A cathode current collector is positioned within the cathode material and the vessel is cooled to a temperature sufficient to solidify the cathode material. The vessel is sealed by positioning a lithium cap on the solidified material and cold welding or diffusion bonding the cap under pressure to the receiving vessel to form a lithium anode encasing member.
Further improvements have been made in such cells which include embedding the cathode lead within the anode encassing member as well as facitilating the manufacturing thereof. See U.S. Patent Application Ser. No. 716,339, filed Aug. 20, 1976, and assigned to the assignee of the present invention.
The present invention incorporates all of the advantages provided in the prior invention and includes as a further object an improved method of fabricating the encasing member so as to eliminate the need to freeze the cathode material. The present invention utilizes a vise to pinch the flaps of the anode encasing member together to form a cold weld. The pinched area is thereafter folded and, while in a die, flattened against the soft cathode material.
While the present invention is especially well suited for use in the manufacture of lithium-halogen batteries, and is therefore described in particularity with respect to such batteries, the invention is also useful in the manufacture of lithium envelopes for encapsulating corrosive materials such as solid depolarizers and electrolytes.